Tea and Health Continued

More on Tea and Health

An article in the US National Library of Medicine outlines the composition of green, oolong, and black teas:

“Tea is manufactured in three basic forms. Green tea is prepared in such a way as to preclude the oxidation of green leaf polyphenols. During black tea production oxidation is promoted so that most of these substances are oxidized. Oolong tea is a partially oxidized product. Of the approximately 2.5 million metric tons of dried tea manufactured, only 20% is green tea and less than 2% is oolong tea… Fresh tea leaf is unusually rich in the flavanol group of polyphenols known as catechins which may constitute up to 30% of the dry leaf weight. Other polyphenols include flavanols and their glycosides, and depsides such as chlorogenic acid, coumarylquinic acid, and one unique to tea, theogallin (3-galloylquinic acid)… The amino acid theanine (5-N-ethylglutamine) is also unique to tea… [Tea contains] a series of compounds, including bisflavanols, theaflavins, epitheaflavic acids, and thearubigens, which impart the characteristic taste and color properties of black tea… There is no tannic acid in tea. Thearubigens constitute the largest mass of the extractable matter in black tea… The catechin quinones also initiate the formation of many of the hundreds of volatile compounds found in the black tea aroma fraction.”